The invention herein disclosed and claimed pertains generally to cables which are adapted to convey both information signals and electric power. More particularly, the invention pertains to improvements in such cables for reducing wear or other mechanical deterioration thereof.
To operate a remotely controlled vehicle such as a tethered vehicle, it may be necessary to couple both control signals and power thereto, and various designs are presently available for an electrically conductive cable through which both signals and power may be simultaneously conveyed to the vehicle from a command station. In such combination cables a coaxial cable, through which control or other information signals may be transmitted, may be encased together with two or more electrical conductors, which are large enough to carry substantial amounts of electric current. The cable may also have to include strengthening means to meet a minimum tensile strength requirement, and if used in a marine environment, e.g. to tether a remotely controlled underwater vehicle, may require flotation or other devices to achieve a specified buoyancy.
In addition to the above requirements, a combination cable may have to have a minimum bend radius under tension to be useful in certain important applications. For example, to enable efficient storage, deployment or recovery, the cable may have to be sufficiently flexible to be wound upon a drum or to pass over a sheave. If the cable does not have sufficient flexibility for such operating conditions, wear or other mechanical deterioration will be hastened. Yet the other aforementioned requirements, for strengthening and buoyancy means encased together with separate signal and power conductors, may serve to reduce flexibility.